Arsène Wenger last night dismissed Sir Alex Ferguson's claim that Arsenal are a club in transition and claimed his side are equipped to mount a challenge for the Premiership this season. The Arsenal manager, in buoyant mood after Emmanuel Adebayor's goal five minutes from time secured a first victory at Old Trafford in the league since May 2002, claimed critics had been too quick to rule out their chances of entering the title race after a slow start to the domestic campaign.

"There were a lot of questions raised about us, about team spirit, and the fact that we won the game says a lot about the strengths of the team," said Wenger. "I don't feel we are in transition at all. I'm at Arsenal Football Club; that means we are very ambitious. We were in the final of the Champions League last year with nearly that team, not conceding a goal and you see why today.

"Everybody has written us off straight away, if you open the newspapers we'd be playing [in the Championship] next year. We're very ambitious. We want to win the title. I believe we can but we need performances like that."

Arsenal's belligerent display belied their slow start to the season. Wenger admitted that the opening three league matches, when Arsenal had collected only two points, had prompted much introspection. "It was a tricky experience because I'm not stupid enough to think that nothing can happen to us," he said. "I've seen players who are very good, when the doubt creeps in they become suddenly average - even very good players."

A Manchester United victory would have extended their lead over Arsenal to 13 points, although that outcome never looked likely as the visitors' midfield triumvirate of Tomas Rosicky, Gilberto Silva and Cesc Fábregas controlled play for long periods. Fábregas was particularly instrumental, robbing Cristiano Ronaldo of possession before sidestepping a couple of challenges and feeding Adebayor for the Arsenal goal. "He was outstanding," said Wenger of the young Spaniard.

Wenger also saluted Adebayor's contribution after the 22-year-old striker made light of Thierry Henry's absence through injury up front. "Thierry is a world-class player and we need him but it's a team sport first and Adebayor brought to the team today exactly what we needed," he said. The Togo international also won an early penalty that Gilberto Silva failed to convert after Tomasz Kuszczak produced a fine stop to atone for bringing down Adebayor. Kuszczak's display was one of the few bright spots for Ferguson.

The United manager, in a rare show of magnanimity, had no complaints about the result. "Arsenal deserved to win the match," said Ferguson. "I thought that in the last 25 minutes they were a lot stronger."

He admitted that defeat, United's first of the season, ending their 100% record in the Premiership, spelt out the size of the task ahead. "It's a very difficult league," said Ferguson. "It's Arsenal's first win, our first defeat, Chelsea have lost a game, Liverpool have lost two. It just shows it's not going to be easy."